1. Field of the Invention
This invention relates generally to shaft bearings, and is concerned in particular with an improvement in the bearings used to support the rotatable and axially reciprocative shafts or journals of doctor blade support structures in web handling machines of the type typically found in paper and textile mills.
2. Description of the Prior Art
Many machines in the paper, textile and other industries employ rotary cylinders or drums as an integral part of web handling or processing operations. In many of these machines it is necessary to provide a means by which to remove built up contaminants or to remove the web from the surface of such cylinders and this is usually accomplished by contacting the cylinder surface with a structurally supported blade, creating a scraping or wiping action. The blade length is normally equivalent to the face length of the cylinder to be cleaned. Often the supporting structure and the blade are moved parallel to the cylinder axis, a distance of less than one inch, in a reciprocating motion to cause a more even wear distribution on the roll surface and blade tip.
In modern machines, the blade support structure or beam can be quite massive in size and weight. Structures up to 400 inches wide and weighing several tons have become quite common in some machines used in the paper industry. Supporting bearings for such structures have been a major consideration because of lost production and cost of repair time in the event of bearing failure.
Many machine processes expose bearings to harsh environments that often include high-temperatures, wet conditions, and chemical wash-downs. Such adverse conditions have a detrimental effect on the life expectancy of the bearings. Seal configuration and lubrication retention are significant design considerations.
In most applications, blade support structures require two modes of movement. The first, already mentioned, is the cross-machine reciprocating motion which is often five to ten cycles per minute. The second mode is a rotational motion allowing the blade to be positioned against the roll surface and then retracted to facilitate blade replacement when necessary.
The cross-machine, or reciprocating motion, is considered to be the "primary" mode due to the large number of cycles accumulated over long operating periods. A cycle rate of six strokes per minute will total over 3,000,000 cycles in a one year period of twenty-four hours per day operation. By way of contrast, rotational motion is normally one to four times per day, accumulating only 365 to 1460 load/unload cycles per year.
Bearing self-alignment capability is a major consideration due to initial "machined-in" and ongoing thermal changes in the blade support structure.
Another major concern is the amount of time required to replace or repair a worn or damaged bearing and the resulting cost of lost production.
In many instances, conventional bearings must be completely removed from the blade support structure journals or shafts in order to facilitate repair work. This results in loss of accurate positioning and alignment of the blade support structure relative to that machine rotary cylinder or drum, and often involves disassembly of a significant number of components.
An objective of the present invention is the provision of a bearing assembly which can be readily disassembled to accommodate replacement of worn components, without requiring separation of the entire assembly from the supported shaft or journal.
A companion objective of the present invention is the accommodation of the aforesaid disassembly without disturbing a fixed base component of the bearing housing, thus obviating any need to realign the bearing with adjacent machine components following reassembly.